We carry out the Lie group classification of the generalized Lane–Emden equation
xu00 þ nu0 þ xHðuÞ ¼ 0, which has many applications in mathematical physics and astrophysics.
We show that the equation admits a three-dimensional equivalence Lie algebra.
It is also shown that the principal Lie algebra, which in this case is trivial, has seven possible
extensions. Three new cases arise for which the Lie point symmetry algebra is nontrivial.
Comparison is then made of these cases with the Noether symmetry cases as well
as the partial Noether operators.